1. Field of the Invention
The present invention relates to a fluid pressure booster including: a control piston in which brake operation input from a brake operation member acts in an advancing direction, and reaction based on fluid pressure of a booster fluid pressure generation chamber that generates fluid pressure for actuating a master piston of a master cylinder acts in a retracting direction; a pressure increasing valve provided between the booster fluid pressure generation chamber and a fluid pressure generation source so as to open at the time of advance of the control piston and close at the time of retraction of the control piston; and a pressure reducing valve provided between a release chamber communicating with a reservoir and the booster fluid pressure generation chamber so as to close at the time of the advance of the control piston and open at the time of the retraction of the control piston, the control piston being actuated forward and backward so that the brake operation input and the reaction based on the fluid pressure in the booster fluid pressure generation chamber are balanced to regulate the fluid pressure in the fluid pressure generation source to act on the booster fluid pressure generation chamber.
2. Description of the Related Art
Such a fluid pressure booster has been known from, for example, Japanese Patent Application Laid-Open No. 2002-308085.
In such a fluid pressure booster, an activation load (a force required for opening a valve) of the pressure increasing valve is reduced by setting a small seal diameter. Such setting of the seal diameter, however, reduces response when a brake operation member is strongly operated to introduce high fluid pressure from a fluid pressure generation source into a booster fluid pressure generation chamber. Further, setting a large seal diameter to the contrary increases the activation load of the pressure increasing valve.